1. Field of the invention
The present invention relates to a novel olefinic thermoplastic elastomer composition. More particularly, it relates to an olefinic thermoplastic elastomer composition having excellent property to prevent blooming of various kinds of additives on the surface of molded products and useful in the fields of automobiles and light electrical appliances.
2. Description of the prior art
Olefinic thermoplastic elastomers are composite materials made by blending of rubbers comprising the hard segment of a polyolefinic plastic, such as polyethylene, polypropylene and the like, and the soft segment of an ethylenic elastomer, such as EPDM and EPM, as the main components or by partial crosslinking of these rubbers in the process of the blending. The olefinic thermoplastic elastomers have been urged to bring them to practical applications as the material to replace polyvinyl chloride resins because they have advantages of no environmental problems, lower specific gravity and better property for recycling.
Particularly when the olefinic thermoplastic elastomers are used as interior materials of automobiles, processes after the T-die extrusion and the calendering can be made much simpler than the processes using polyvinyl chloride resins. Olefinic thermoplastic elastomers are very often used for instrument panels, doors and ceilings because of this reason.
In the olefinic thermoplastic elastomers, relatively large amounts of various additives, such as a process stabilizer, a lubricant, an antioxidant, a light stabilizer, a light absorbent and the like, are compounded for the purpose of enhancing workability and durability of the molded products.
Because large amounts of additives are compounded into the olefinic thermoplastic elastomers, the additives frequently bloom out with passage of time after films and sheets prepared from the olefinic thermoplastic elastomers are formed into final products.
In the olefinic thermoplastic elastomers, additives are compounded in considerably larger amounts than in conventional polypropylene resins and the like for improvement of workability and properties in end-use applications. A large amount of an amorphous component, such as EPM and EPDM, and a mineral oil plasticizer are also compounded in the elastomer in addition to polypropylene. The phenomenon of blooming is caused by these reasons. The blooming of the additives leads to undesirable phenomena, such as unsightly appearance of the products, inferior printing in a later process, poor adhesion and the like, and troubles occur in subsequent processing from these phenomena.